Electroplating Copper Seed Layers on High-Resistivity Substrates
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Solution Overview
Problem
Current methods for producing copper seed layers in microelectronics, such as chemical vapor deposition (CVD) and physical vapor deposition (PVD), face challenges with non-conformal and non-uniform thickness, poor adhesion to diffusion barriers, and high costs, especially in advanced integrated circuits with small feature sizes.
Innovation Solution
A specific electrodeposition process involving a 'cold entry' and 'hot exit' stage, where the substrate is initially contacted with an electroplating bath without polarization for at least 5 seconds and then separated under electrical polarization for 1-10 seconds, using a bath with copper ions and complexing agents like pyridine and 2,2' bipyridine, to achieve continuous and conformal copper seed layers with excellent adhesion on high-resistivity substrates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If PVD or CVD is used to deposit copper seed layers, then adhesion to barrier layers is improved, but manufacturing cost increases and layer uniformity deteriorates
Solution Approach 1:
The patent replaces physical vapor deposition (PVD) and chemical vapor deposition (CVD) processes with an electrochemical electrodeposition process. This substitution uses electrochemical reactions instead of physical vapor condensation or chemical vapor phase reactions, enabling copper seed layer deposition at lower cost while achieving uniform thickness and adequate adhesion through controlled electrochemical mechanisms
Solution Approach 2:
The patent modifies the electrodeposition process parameters specifically for high-resistivity substrates by implementing a two-stage approach: initial contact without polarization to enable nucleation on insulating surfaces, followed by polarization to achieve uniform copper deposition. This parameter modification allows electrodeposition to work on substrates with sheet resistance up to several mega ohms per square
2Strength
If PVD is used to deposit copper seed layers, then adhesion to barrier layers is improved, but layer uniformity and conformality deteriorate
Solution Approach 1:
The patent replaces physical vapor deposition (PVD) with electrochemical electrodeposition. Unlike PVD which suffers from line-of-sight deposition and shadowing effects causing non-uniform layers, electrochemical deposition occurs uniformly across the entire substrate surface through ionic conduction in electrolyte, achieving conformal and uniform copper seed layers even on complex topographies
Solution Approach 2:
The patent implements continuous agitation of the electrolyte solution during electrodeposition to maintain uniform copper ion distribution around the substrate. This continuous action prevents local depletion of copper ions and ensures uniform deposition rate across the entire surface, achieving superior layer uniformity compared to batch PVD processes
3Ease of manufacture
If conventional electrodeposition is used on high-resistivity substrates, then manufacturing cost is reduced, but process feasibility deteriorates due to ohmic drop
Solution Approach 1:
The patent implements a preliminary action by initially contacting the high-resistivity substrate with the electrodeposition electrolyte without applying polarization. This initial contact period allows formation of conductive pathways and reduction of surface resistance, preparing the substrate for subsequent polarization and uniform copper deposition, thereby enabling the process to work on substrates with sheet resistance up to several mega ohms per square
Solution Approach 2:
The patent segments the electrodeposition process into two distinct stages: (1) initial contact without polarization for nucleation and resistance reduction, and (2) polarization stage for uniform copper deposition. This segmentation allows each stage to be optimized independently, making the overall process feasible for high-resistivity substrates where conventional single-stage electrodeposition would fail due to ohmic drop
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This process enables the production of copper seed layers with thicknesses of 10 nm or less, ensuring high adhesion and conductivity, suitable for subsequent filling processes, even on substrates with resistivities up to several mega ohms/square, thereby improving the reliability and efficiency of copper interconnections in microelectronics.
Implementation Method 1
the substrate is initially contacted with an electroplating bath without polarization for at least 5 seconds
Implementation Method 2
then separated under electrical polarization for 1-10 seconds, using a bath with copper ions and complexing agents
Data Source
Figure 1A
Figure 1B
AI summary
The invention concerns an electroplating method for coating a substrate surface with copper. The invention is characterized in that said method includes: a step whereby said surface to be coated is contacted without electrical polarization with an electroplating bath; a coat forming step whereby said surface is polarized; a step whereby said surface is separated from the electroplating bath under electrical polarization; said electroplating bath comprising dissolved in a solvent: a source of copper ions, in a concentration of 0.4 to 40 mM; at least one copper complexing agent.